Probing Through-Space Polar-π Interactions in 2,6-Diarylphenols

Area of Science:

• Organic Chemistry
• Physical Chemistry
• Computational Chemistry

Background:

• Phenol acidity is typically modulated by substituents through electronic effects transmitted via chemical bonds.
• The influence of through-space interactions on phenol acidity remains largely unexplored.
• Understanding these non-bonded interactions is crucial for predicting and controlling molecular properties.

Purpose of the Study:

• To investigate the role of through-space effects on the acidity of substituted 2,6-diarylphenols.
• To elucidate the contribution of OH-π and O⁻-π interactions to proton affinities and acidity trends.
• To provide experimental and computational evidence for the significance of non-bonded interactions.

Main Methods:

• Integrated experimental and computational studies were performed.
• Substituted 2,6-diarylphenols were synthesized and characterized.
• Proton affinities and acidities were measured and calculated.
• Through-space interactions (OH-π and O⁻-π) were analyzed.

Main Results:

• Through-space OH-π interactions were identified as a key factor influencing phenol acidity.
• O⁻-π interactions were found to play a significant role in the stability of the phenoxide anion.
• Observed trends in proton affinities and acidities correlated with the strength of these through-space interactions.
• Computational modeling supported the experimental findings, quantifying the interaction energies.

Conclusions:

• Through-space interactions are essential contributors to the acidity of 2,6-diarylphenols.
• The study clarifies the poorly understood role of non-bonded effects in modulating phenol acidity.
• Findings provide a new perspective on substituent effects in phenols, emphasizing spatial arrangements.